Our goals will be: 1) to investigate how steroids are concentrated in the internal spermatic artery of rat and other animals by examining the dynamics of venous-arterial transfer of steroids in the pampiniform plexus, by comparing this transfer in various species and by exploring the fate of steroids after transfer; 2) to investigate the metabolic environment of the rat and rabbit testis and epididymis by studying the rate of respiration, uptake and release of endogenous substrates and metabolic end products, by determining the role of glucose and palmitate in testis and epididymis in vivo, by determining the role of the pampiniform plexus and the epididymal fat pads and by developing techniques for long term monitoring of hemodynamic, metabolic and endocrinologic parameters; 3) to investigate control of blood flow and distribution in the testis and epididymis by measuring basic hemodynamic parameters and vascular reactivity, determining the effect of testicular nerve stimulation on pressure-flow relationships, exploring the serotonin-induced constriction of the internal spermatic artery, measuring arterial-venous shunt flow, investigating a role for testis and pituitary hormones and exploring hemodynamic responses to gas tensions and glucose levels. To achieve these goals we will use intact in vivo preparations, in sito perfusion and autoperfusion of the testis and epididymis and analytical techniques including high pressure liquid chromotography, gas chromotography, mass spectroscopy, radioimmuno assay, liquid scintillation spectrometry and autoradiography. We expect that these studies will increase knowledge of the male reproductive organs, permit a more critical evaluation of in vitro data, suggest ways of delivering known antifertility compounds so that their effectiveness is enhanced and suggest new approaches to selective and reversible inhibition of germ cell function.